The invention is in the field of methods for preparing crosshead extrusion tips and dies for melt extrusion.
Crosshead extrusion is the normal method for jacketing a communications element, such as copper wire or optical fiber, with plastic. A die has an internal bore through which the communications element is pulled. Plastic melt is introduced in the extrusion process around the tip and the communications element, the aggregate proceeding through the bore of a die which has an internal bore determining the external shape of the plastic jacket.
In order to obtain the maximum protection of the communications element by using the minimum amount of plastic melt, it is necessary to center the tip with respect to the die. Centering has formerly been accomplished by trial and error methods involving the extrusion of a cable sample which is then severed to examine the relative thickness of the jacket around various points on the periphery of the communications element. If the communications element is not centered properly, adjustments are made to rectify the situation.
While the former method above described is time consuming, it has also become more and more expensive in an era of cables having greater numbers and packing densities of communication elements per area of a cable cross-section. The number of communication elements that must be severed makes taking samples more expensive, and the precise tolerances required for bulk splicing of multifiber optical cables demands improved performance in the positioning of communication elements within tubes or ribbons.
Therefore, an object of the invention is to provide an improved crosshead extrusion set up process which can be carried out more quickly and with better results than previous methods.